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The TSA agent suspected of threatening LAX may have sent more packages, and federal officials are running down every lead to make sure that the threats were isolated and idle. Kim Baldonado reports from Westwood for NBC4 News at 11 on Sept. 11, 2013. (Published Thursday, Sept. 12, 2013)

A former TSA employee who worked at Los Angeles International Airport was arrested Tuesday night after he allegedly made threats to terminals and left a suspicious package at the airport the same day he quit his job, the FBI announced early Wednesday as a bomb squad conducted a search in connection with the investigation.

Nna Alpha Onuoha, 29, a U.S. Army veteran from Inglewood, resigned from the Transportation Security Administration (TSA) on Tuesday -- a position he has held since 2006 -- and left a package later that afternoon at the TSA's LAX Headquarters addressed to another TSA employee, according to an FBI statement.

Ex-TSA Agent Visited LAX Before Arrest

Before a rogue ex-TSA agent was arrested on suspicion of making terrorist threats at LAX, he reportedly showed up at the airport in plain clothes, appearing to be examining three different lobbies. Robert Kovacik reports from LAX for NBC4 News at 11 p.m. on Sept. 11, 2013. (Published Thursday, Sept. 12, 2013)

The package was treated as suspicious and inspected by a Los Angeles Police Department bomb squad, but it only contained an eight-page letter detailing his disdain for the United States and other opinions about what led to his suspension and ultimate resignation.

Hours later, a man believed to be Onuoha called the TSA and told employees to "begin evacuating certain terminals at the airport" and said he would "be watching" to see if they followed his instructions, the statement read.

FBI Agents Track Down LAX Threat Suspect in Riverside

Federal Agents spent hours scouring through ex-TSA screener Nna Alpha Onuoha’s mini van for evidence Wednesday. Investigators say a church security guard spotted a man sleeping inside a minivan, and then asked him to leave, which lead to officers stopping the vehicle. Tony Shin reports from Riverside for the NBC4 News at 5 p.m. on September 11, 2013. (Published Wednesday, Sept. 11, 2013)

The terminals were cleared per his threats, but no threat to the airport was found.

Officials with the Joint Terrorism Task Force went to Onuoha's Inglewood apartment and found nothing except a note taped inside of his closet with an "unspecified threat" citing the Sept. 11 terrorist attacks anniversary.

Residents React to Arrest of Ex-TSA Employee

The investigation involving Nna Alpha Onuoha, a former TSA worker accused of making threats involing LAX, stretches from the airport to an apartment in Inglewood and a church in Riverside. Toni Guinyard and Jacob Rascon report for the NBC4 News at Noon on Wednesday Sept. 11, 2013. (Published Wednesday, Sept. 11, 2013)

The letter read, "09/11/2013 THERE WILL BE FIRE! FEAR! FEAR! FEAR!" according to a criminal complaint filed against Onuoha by the United States District Court.

A third suspicious package mailed to a TSA office near LAX was linked to Onuoha, and prompted the office's evacuation Wednesday afternoon.

Ex-TSA Worker Accused of Making Threats

An investigation involving a former TSA screener accused of making threats against LAX focused on the Riverside area Wednesday morning. Toni Guinyard and Jacob Rascon report for Today in LA on Wednesday Sept. 11, 2013. (Published Wednesday, Sept. 11, 2013)

Onuoha served in the U.S. Army from April 2004 to April 2012, earning the National Defense Service Medal, Global War on Terrorism Service Medal, Kosovo Campaign Medal, Army Service Ribbon, Overseas Service Ribbon, Armed Forces Reserve Medal with "M" Device, and Nato Medal.

"As far as the veterans here are concerned, they have seen him every single day," said Ivan Mason, executive director of the U.S. Veterans Initiative. "He works out in our gym, runs around the neighborhood, eats in our cafeteria, and he puts on his uniform on his scheduled days and marches down to the airport."

Neighbors said he lived at the 600-resident veterans complex for at least five years. Residents identified the subject who appears in several photos on the website SatanHasFallen.org as Nna Alpha Onuoha.

The website includes letters in which the author writes about Christianity, the "sin of sexual immorality" and the "end of America."

An Amazon.com listing for a 424-page book titled "The End of America: The End of the World" credits Alpha Onuoha as the author. The summary describes the self-published book as "based on the real-life experiences, thoughts, and observations of an African immigrant, beginning from Africa and ending in America."

Onuoha is being held in custody on suspicion of making terrorist threats -- a violation of both federal and state law -- pending additional investigation, according to the FBI.

Onuoha's first appearance in federal court lasted some 4 minutes Wedneday afternoon. A magistrate ruled the suspect will be held at least until Monday's bond hearing.

The suspect also was involved in a high-profile case in which he allegedly shamed a teen because of her attire, NBC News confirmed. The June "shaming" incident was reported after a blogger wrote about the encounter and posted pictures of his 15-year-old daughter in the attire she was wearing at the time.

Federal authorities told NBC4 the incident was a factor in Onuoha's suspension.

Leads on Onuoha's whereabouts led authorities to Harvest Christian Fellowship Church in Riverside, where Riverside police and members of the Joint Terrorism Task Force arrested Onuoha just before midnight Tuesday. He was found sitting in the vehicle parked in an otherwise empty parking lot, police said.

Additional packages were found inside the church and in Onuoha's car, which was parked outside of the church, Riverside Police Lt. Milby told NBC4. None of the items, which included a Bible and cross, found in the vehicle were deemed hazardous, according to Riverside police.

"We're still trying to figure out what his connection to Riverside is," said Riverside Police Department Lt. Guy Toussaint.

A bomb squad was still at the church Wednesday morning, prompting the church to cancel its private school classes for the day.

Aerial video showed investigators near a minivan with all doors, hood and liftgate open in an Arlington Avenue parking lot. Several explosions, possibly involving the bomb squad investigation, were reported Wednesday morning. Video also showed a red cross with writing on it, similar to one pictured on the SatanHasFallen.org web site.

In light of the events at LAX "involving a disgruntled former airport worker and the 9/11 anniversary tragedy," LAX, Ontario and Van Nuys airports increased patrols by uniformed officers in and around the airports, Los Angeles Airport Police Chief Patrick M. Gannon said in a statement.